Apparatus for the continuous manufacture of curd



Oct. 12, 1965 RADEMA ETAL 3,210,845

APPARATUS FOR THE CONTINUOUS MANUFACTURE OF CURD 2 Sheets-Sheet 1Original Filed July 10, 1961 INVENTORS LAMBEHTUS FADE/W4 JACOB UBBELSADR/AAN GJ ARE/VTZE/V AND JOHAN 7.' VAN DER L/NDE BY 1 m/ ATTORNEYS Oct.12, 1965 RADEMA ETAL 3,210,845

APPARATUS FOR THE CONTINUOUS MANUFACTURE OF CURD Original Filed July 10,1961 2 Sheets-Sheet 2 INVENTORS LAMBERTUS RADEMA JACOB UBBE'LS ADRIAA/VG. J- ARE/VTZEN AND JOHAN 7T VA/VDEH L/NDE BY #MW/ +We ATTORNEYS UnitedStates Patent 3,210,845 APPARATUS FOR THE CONTINUOUS MANUFACTURE OF CURDLambertus Radema and Jacob Ubbels, Ede, Adriaan G. J. Arentzeu,Amersfoort, and Johan T. van der Linde, Ede, Netherlands, assignors, bymesne assignments, to Bedrijven van het Nederlands Instituut voorZuivelonderzoek, Ede, Netherlands, an institution of the NetherlandsOriginal application July 10, 1961, Ser. No. 122,690, new Patent No.3,132,026, dated May 5, 1964. Divided and this application Sept. 7,1962, Ser. No. 227,103 Claims priority, application Netherlands, July11, 1960, 253,654 3 Claims. (Cl. 31-46) This is a division ofapplication Serial No. 122,690, filed July 10, 1961, now Patent No.3,132,026, issued May 5, 1964.

The invention relates to a apparatus for the continuous manufacture ofcurd by adding to cooled milk the required quantity of rennet, keepingthe mixture for some time in that temperature range, and subsequentlyheating it.

Recently there has been a tendency to mechanize the manufacture ofcheese and to carry it out in a continuous process. A particularlyimportant part of such a process is the production of the curd,especially the cut curd.

One of the diificulties involved is, that the curd becomes availablebatchwise, while the further apparatus for the manufacture of cheeseshould preferably operate continuously. As the quantity becomingavailable cannot be processed rapidly enough, it is difiicult to get ahomogeneous product in this way. A resolution of this problem might be areduction of the ratio between the capacity of the cheese tank and thecapacity of the said further apparatus for the manufacture of cheese.Another resolution might be to carry out the coagulation process itselfcontinuously. This later method was suggested in the US. Patent No.2,781,269. However, the process has the disadvantages of (1) requiring alarge tube for the coagulation to take place in, (2) of having a shortmixing time which does not guarantee a homogeneous product, (3) ofrequiring a long time to dampen the turbulence and (4) of not being ableto uniformly cut the curd.

According to Nature 149, 194 (1942) the clotting of milk caused by theaddition of rennet may be divided into two phases, viz, one enzymic andone non-enzymic. Now the temperature coefficient of the first phase wasfound to be much smaller than that of the second phase.

Now, it was found that the difference in temperature coefiicient betweenthe two phases may be utilized for the continuous production of curd.According to the invention rennet, starter, and other ingredientsrequired for the production of cheese are added to the milk that hasbeen cooled down to a temperature of 1 C. to +15 C., and after beingkept at said temeprature for 1 /2-48 hours, this mixture is passedfirstly through a heat exchanger, in which it is heated to 2045 C., andthen through a coagulation chamber, which near the inlet-opening of thefeed pipe comprises a device for preventing turbulences in the liquidmass and the outlet opening may be equipped with an apparatus forcutting the curd.

Since during the first phase the consistency of the milk does not changeand no flocculation takes place as yet, the milk may still be made toflow, be pumped, or be mixed as desired, without any detrimentalconsequences. It is thus possible to mix the commonly used additionsvery thoroughly with the milk, during the whole cold storage period, ifdesired. This promotes the homogeneity of the product. The mixingprocess preferably takes place with the exclusion of air. Indeed, largeamounts of air may dissolve in cold milk, and this air will be liberatedagain during the heating process. It may be occluded by the clottingcasein and may afterwards cause the curd to float in the whey and mayproduce air occlusions in the cheese.

The circumstance that the clotting time becomes only slightly shorter ifafter the completion of the first phase the milk is still stored at thelow temperature enables that the heaing of the curd does not have totake place immediately after the completion of the first phase. Thisimplies in the first place that if the milk is fed continuously to anapparatus in which the first phase is completed, the time during whichthe milk remains in said apparatus above a given minimum is not tieddown to narrow limits, so that the control of this part of the processpresents few difficulties. Secondly this even enables one to carry outthe first phase discontinuously in tanks. In that case the temperatureof the milk should be adjusted so that after the simple addition andmixing of the commonly used ingredients the end-point of the first phaseis indeed reached, but that the clotting time decreases only within apermissible range during the period in which the liquid from the tank isprocessed further.

The method at which the reaction of the first phase takes place in tanksinstead of in a heat exchanger greatly promotes the homogeneity. In thisway the dosage of the additions and the temperature-control are simple.

The apparatus for carrying out the process comprises connected insequence means for cooling, mixing and holding of the milk and addedingredients, pumping means, means for warming the milk mixture tocoagulating tem perature, and a coagulation chamber with means at itsinlet end for rapidly changing the turbulent stream of warmed milk intoan undisturbed and slowly moving stream of coagulating milk at uniformspeed and with means at its outlet end for cutting the slowly movingstream of curd.

In the heat exchanger the mass is heated to the clotting temperature andsubsequently flows into the coagulation chamber, in which, movingslowly, it completes the second phase. The time interval between thebeginning of the heating process and the moment at which the milk in thecoagulation chamber is moving uniformly with an equal and similarlydirected velocity has to be so short that no perceptible clotting occursduring this time interval. Indeed, turbu'lences of the clotting milk aremost undesirable; they give rise to the dreaded curd dust as well as tolosses of fats and proteins.

Preferably the process is started with milk having a temperature of 3-6C., and after addition of the rennet, starter, and the furtheringredients the mass is kept at said temperature for another 2-6 hours.

The heat exchanger used may consist of a conduit or tube heated by steamor some other heating medium, but preferably a tubular or a plate heatexchanger is used. The most favourable temperature for the coagulationin the coagulation chamber is 2930 C.

The cut curd thus obtained may further be converted into cheese.

Referring now to the drawings:

FIG. 1 is a diagrammatic side elevation of a suitable apparatus for thecontinuous production of curd.

FIG. 2 is a partial fragmentary view of perforated discs 7 and 8 withrespective openings 11 and 12.

FIG. 3 is a perspective view of the upper part of the coagulationchamber 5 illustrating the cutting means 9.

FIG. 4 is an auxiliary drawing to derive the proper position in whichthe cutting means are to be placed to cut and remove curd outwardly.

FIG. 5 is a diagrammatic drawing of the curd strips formed by thecutting means.

In FIG. 1, 1 denotes a tank in which the cold milk is stored and therequired addition is made of rennet and other substances used in makingcheese curd such as calcium chloride, saltpetre, starter culture and/orcoloring agent. The said ingredients are thoroughly mixed therein bystirring. After the desired reaction period, the mixture is pumped bypump 2 via lines 4 through heat exchanger 3 into the inlet opening inthe center of bottom plate 6 of coagulation chamber 5. At a very shortdistance above bottom plate 6, the flow of milk is interrupted by twoperforated discs 7 and 8 whose respective perforations 11 and 12 arestaggered as shown in FIG. 2 whereby the flow of coagulating milkbecomes slow and uniform to the top of the coagulation chamber 5. In thecenter of the coagulation chamber is a smaller cylinder 10 which extendsabove the top of the coagulation chamber. Attached to the upper end ofcylinder 10 is the cutting apparatus 9 which rotates in the direction ofthe arrow.

FIG. 2 illustrates the size and staggered position of the respectiveperforations 11 and 12 in discs 7 and 8. The size and number of theperforations 11 in lower disc 7 are such that a pressure is set upbeneath this disc which is large in relation to the pressure lossescaused by friction of the warmed milk between disc 7 and bottom plate 6.Suitable perforations would be fifty 1 mm. diameter perforations per 100cm. of disc 7. This ensures that the quantity of milk flowing througheach of the perforations of disc 7 is about equal. The upper disc 8contains an equal number of perforations 12 in the same pattern but theyare much larger, i.e., fifty 10 mm. diameter perforations per 100 cm.and are staggered with respect to the perforations 11 of the lower disc7. The upper disc 8 prevents any secondary flow in the coagulating milk.

FIG. 3 illustrates the cutting means 9 of FIG. 1 which is rotated aboutcylinder 10 by rotating shaft 14 so that cutting edge 15 and verticalblades 16 cut the curd into strips. The knife 9 is part of a sector of acircle and has been mounted in such a way that the cutting edge 15 or ABforms a small angle with the plane through the upper edge 18 of cylinder5, so that point A lies higher than point B. The cutting surface ABC ofthe rotating knife may remain just inside the wall of the cylinder, orit may overlap the wall of the cylinder as shown. The circular edge BCof the knife is inclined upwards in a helix in such a way that theunderside of the plate ABC remains free of the continuously risingsurface of the coagulated milk. The strips of curd formed by means ofthe cutting edge 15 and blades 16 slide over plate ABC in a way which isillustrated diagrammatically in FIG. 5. Thus, they remain intact, butare straightened out. If AB were horizontal, the innermost strip wouldbrush against the wall CAD (the radius of curvature of wall CAD beinglarger than the curvature of the inner cylinder) and at the same timewould have to go up the slope of plate ABC (for C lies higher than A andB). Actually, as already mentioned above, A lies higher than B, so thatthe slope up which the central strip has to go is smaller. Anotherobject thus attained is that the cut strips will tend to slide offsideways, in consequence of which the pressure of the innermost stripagainst the wall CAD, among other things, will diminish. At an adequateslope of AB, the innermost strip may even be free from this wall. Thefirmness of the cut strips also plays a part in this. The less firm thestrips, the more readily they tend to slide off sideways with the sameposition of plate ABC.

The position of plate ABC is preferably adjusted in such a way that thestrips only just do not slide off sideways. As they arrive at the edgeof the outer cylinder the strips are cut up by the vertical blades 17.Since all the strips are cut into n pieces with each revolution of thecutting apparatus if there are n blades on the circumference of theupper edge 18, the volume of a piece from 4 the strip originally lyingat a distance r from the center as in FIG. 4, the Width of the stripbeing 11 and its height h, is equal to n If care is taken that rb isconstant, the volume of all the pieces formed will be equal. The shapeof the pieces is mainly determined by the movement of the stripsrelative to the blades 17.

In FIG. 4 the construction is stated of the speed V of a strip of curd,relative to the knives 17 of the upper edge 18 of cylinder 5. If V isthe speed of the rotating cutting apparatus at the outer cylinder, thatis, on radius R, one may construct the speed V, in respect of thecutting apparatus of a strip on radius r. Then ZLL V, R

At its movement over the plate of the cutting apparatus the strip willmaintain this speed V The direction of V in respect to the movingapparatus at the moment this strip meets the edge 18 of the outercylinder 5 is the direction of the tangent to the centerline of thestrip, provided that the strip does not slide down sidelongly. In thatpoint the rotating cutting apparatus still has a speed V relative to theouter cylinder edge 18. Thus the speed of the strip in respect to theknives 14 on the edge of the outer cylinder is that indicated by thevector sum V of V, and V,. The angle 1/ between V and V is at a givenform of the wall CAD (vide FIG. 3) depending on the ratio r/R. Theposition of the vertical knives 17 (vide FIG. 5) is fixed so that theymake an angle with V approximating the mean value of 1/.

FIG. 5 shows the position of the blades 17 as Well as the shape of thelumps into which the strips are divided. FIGS. 4 and 5 also show thelength a of the lumps into which a strip is divided by the blades 17 atintervals of I. From the similarity of triangles it follows that Thevolume of a lump is equal to abh if h is the height of the strip. Andsince abh hbr all the lumps obtained have the same volume if [Jr isconstant. The distance between the blades 16 is thus inverselyproportional to the distance of the blades from the centre. The minimumdistance between the blades 17, i.e. between the outer blades, is about0.5 cm. The maximum distance is preferably chosen no greater than 4 cm.

The gradient of AB may in general be between 0 and 60, but preferablybetween 5 and 10, e.g. 7. The pitch of the curved line BC is determinedonly by the speed of the cutting apparatus and the rising rate of thecoagulated milk. In fact, the underside of the plate ABC should alwaysremain free of the rising surface of the coagulated milk. The shape ofthe wall CAD may vary widely; in fact, it may curve forward, or beplane, or curve backward, both vertically and in a diverging direction.If the gradient of AB is sufficient, the wall CAD may even be omittedaltogether. In FIG. 3 the cutting edge AB lies in a plane through theshaft of cylinders 5 and 10. This of course is not necessary.

In the construction described above the cut curd is removed outwards. Itis, however, also possible to remove the curd inwards, i.e. towards theinner cylinder. A combination of the two methods is of course alsopossible and presents possibilities especially when the distance betweenthe inner and the outer cylinder is large.

The side AD of the raised part of the knife rotates as close to theinner cylinder 10 as possible. This inner cylinder has been provided inorder to prevent the cutting speed of the cutting edges relative to thecoagulated curd becoming too slow. Too slow a cutting speed gives riseto all sorts of ditficulties, such as curling-up in front of the knife,poor removal from the knife, and the like.

The cut curd obtained in the above way may be warmed a few degreeshigher to accelerate the syneresis.

The minimum distance between the cylinders 5 and 10 is 1 to 2 cm., themaximum distance is theoretically unlimited, but in practice will notexceed 100 cm.

The minimum diameter of the inner cylinder 10 is cm., i.e. this cylindermay be omitted, if desired; the maximum diameter is not tied down to anylimits, but should always be smaller than the diameter of the outercylinder 5.

In the above description the reference was invariably to an annularcoagulation chamber. Another form may also be used, provided thecoagulation process is not adversely affected by it. A slit-shapedcoagulation chamber makes it possible to use a reciprocating cuttingapparatus, and this is attractive indeed from the point of view ofcutting technique.

In general all the blades should be as thin and sharp as possible. Themaximum thickness might be put at mm. Blades of 0.5 mm. and sheet steelof 1 mm. for the surface ABC are suitable in practice.

Example I In a tank, pasteurized milk was stored at a temperature of 3C. To this milk the following ingredients were added: 6% (by volume) ofstarter, 0.3% (by vol.) of rennet, 0.3% (by vol.) of CaCl 0.2% (byweight) by KNO Five hours after the addition of rennet and starter, themilk was begun to be pumped from the tank and to be forced through aplate-heat exchanger to the coagulation chamber. The milk was heated to30 C. in the heat exchanger. Within 14 minutes after the temperature of30 C. had been reached the milk had risen to the top of the coagulationchamber (height more than 1 m.), where it had a consistency such that itcould be cut. The curd particles thus formed were regularly shaped andwere converted into cheese.

Example 11 The treatment of the milk in the storage tank was the same asin Example I. In the heat exchanger the milk was now heated to 32 C.instead of 30 C. At this coagulation temperature the milk after 6minutes already had a consistency such that it could be cut andconverted into cheese. In this case the height of the coagulationchamber could be less than, e.g. 1 m., and amounted to about 0.5 m.

Example III In a tank, pasteurized whole milk was stored at a temperature of 3 C. The same ingredients as in Example I Were added to thismilk.

After the rennet and the starter had acted on the milk for 36 hours, themilk was begun to be pumped from the tank and to be forced through theplate heat exchanger to the coagulation chamber The milk was heated inthe heat exchanger to 29-30 C. Within 14 minutes after the coagulationtemperature had been reached the mlik rose to the top of the coagulationchamber (height more than 1 m.), where it could be cut. The cut curd wasconverted into cheese.

What we claim is:

1. An apparatus for the manufacture of curd comprising means for storingand mixing cold milk with rennet and starter, pumping means connectedwith the storing means for mixing and moving the mixture therefrom to ameans for warming the milk mixture to coagulating temperature and anopen top coagulation chamber vertically disposed with a bottom inletwith at least two vertically spaced upper and lower perforated discspositioned near the bottom portion thereof with staggered perforationstherein to dampen the turbulence of the milk stream, said perforationsbeing larger in the upper disc and cutting means at the top portion ofthe coagulation chamber for cutting the slowly moving stream and curd.

2. The apparatus of claim 1 wherein the lower perforated disc containsabout fifty 1 mm. diameter perforations per cm. and the upper perforateddisc contains about fifty 10 mm. diameter perforations per 100 crn.

3. The apparatus of claim 1 wherein the cutting means comprises asector-shaped cutter sloping upwards in a helical plane, substantiallyvertical blades at the cutting edge of the sector shaped cutter whosecutting surfaces are on the same side as the cutting edge andsubstantially vertical blades on the circumference of the coagulationchamber whose cutting surfaces are directed into the coagulationchamber.

References Cited by the Examiner UNITED STATES PATENTS 2,717,212 9/55Hensgen et a1. 2,908,575 10/59 Spiess et al. 3146 X 2,917,827 12/59Lankford 31-46 SAMUEL KOREN, Primary Examiner.

CARL W. ROBINSON, HUGH R. CHAMBLEE,

Examiners.

1. AN APPARATUS FOR THE MANUFACTURE OF CURD COMPRISING MEANS FOR STORING AND MIXING COLD MILK WITH RENNET AND STARTER, PUMPING MEANS CONNECTED WITH THE STORING MEANS FOR MIXING AND MOVING THE MIXTURE THEREFROM TO A MEANS FOR WARMING THE MILK MIXTURE TO COAGULATING TEMPERATURE AND AN OPEN TOPCOAGULATION CHAMBER VERTICALLY DISPOSED WITH A BOTTOM INLET WITH AT LEAST TWO VERTICALLY SPACED UPPER AND LOWER PERFORATED DISCS POSITIONED NEAR THE BOTTOM PORTION THEREOF WITH STAGGERED PERFORATIONS THEREIN TO DAMPEN THE TURBULENCE OF THE MILK STEAM, SAID PERFORATIONS BEING LARGER IN THE UPPER DISC AND CUTTING MEANS AT THE TOP PORTION OF THE COAGULATION CHAMBER FOR CUTTING THE SLOWLY MOVING STREAM AND CURD. 